BITwave Virtual Array Handsfree Carkit
BITwave, The Leader In Audio Input Technology presents - The World Smallest: "Virtual Microphone Array" for Noise and Acoustic Echo Cancellation.
BITwave Private Limited has announced the launch of a new "Virtual Microphone Array" technology. This new invention presents a wide range of speech input system applications for devices such as personal mobile systems (3G phone, PDA phone and tablet etc.), industrial eyewear, safety and military helmets etc. The motivation behind the technology for developing these applications demonstrates BITwave's commitment in developing cutting edge audio input technology and devices for the world's Civilian and Military systems that can add values to our living standards and save lives.
A/P SK Hui, President/CEO of BITwave Private Limited said "I believe that people not only need a smooth transition from home, to vehicle, to office, and anywhere in between, but more importantly, to communicate safely. An integral part of my vision is to incorporate cutting edge technology in military audio capturing and noise cancellation with affordable Bluetooth technology for consumer use. BITwave is committed in strengthening its consumer portfolio using a Tactical to Practical approach that will position BITwave as the leading provider of the next generation of speech input communication platforms in this technology area."
The patent pending "Virtual Microphone Array" developed by BITwave, allows the user to communicate with crystal clear speech quality even in noisy environments and massively double talk situations. It is specially invented for small communication devices such as mobile phones, single piece BT hands-free speakerphones etc. These small communication devices present challenges where the microphones are located just next to the loudspeakers due to space constraints. Full duplex communications with high speech quality in the past is practically impossible until the advent of this technology.
The fundamental behind this technology is having a real physical microphone and one or two virtual microphones. The virtual microphone is modeled after a real microphones' transfer function in all dimensions. The real physical microphone and a virtual microphone create a virtual beam that point towards the user's direction. Simultaneously, a virtual null is created through iterative learning that effectively removes the interference signal, in this case the echo. The user's speech can then be captured and transmitted in the highest quality without echo and noise, enabling the user to have true hands-free conversations.
The "Virtual Microphone Array" offers unparalleled advantages to current existing technology. One of the current technologies available includes the "Small Microphones Array" (see ref. article 1, 2, 3 & 4). This technology requires two physical microphones which require its physical placement to be constrained by the physical space available on the device. This so called "Small Microphone Array" creates a fixed beam in the look direction that constrains the user position with respect to the array. A null can be created in the back plane that is defined as an interference source direction. The interference source level may be reduced using this method.
Figure (1) and (2) show the two systems, its microphone location, loudspeaker location and the beam pointing direction. In Figure (1), for "Virtual Microphone Array" system, the loudspeaker is almost 0cm from the microphone. The output level from the loudspeaker is adjusted to just exceed 90dB. This is to ensure that clear speech can be heard by the user in noisy automotive environments. Figure (2) is a typical "Small Array" speakerphone system. The two microphones are separated by a couple of centimeters and the loudspeaker is about 4 cm from the microphone. The volume for this system was also set to the maximum possible level which is closed to the 90dB level.
Figure (3), (4) and (5) are the real-time recorded audio files which illustrate the differences in performance between a "Small microphone Array" and a "Virtual Microphone Array" in an audio conference situation. A talking head is used to do all the recording. This was to ensure that the two systems were tested under exactly the same situation. The difference in performance between the two will be immediately clear by listening to these recorded audio files.
The "Virtual Microphone Array" has been tested extensively in an automotive environment. As only one microphone needs to be used, it can be implemented with no changes to designs of existing systems. This approach helps to save materials, cost, space and more importantly helps to protect the environment.
The patented (pending) "Virtual Microphone Array" is so versatile it can be integrated in a wide variety of personal devices such as a small ultra-portable BT speakerphone, mobile headsets and single piece BT hands-free speakerphone as shown in Figure (1).
BITwave is a high-tech R&D company specializing in the design and development of DSP hardware and digital signal processing algorithms for real-time adaptive acoustic echo cancellation, multi-channel audio signal processing, speech recognition, microphone array, etc. Our mission is to transform leading edge technology and latest research findings into consumer products for the mass market.
The web address is: www.bitwave.com.sg.
(1)M Dorbecker, Speech Enhancement using small microphone arrays with optimized directivity, in International Workshop on Acoustic Echo and Noise Control, pp 100-103, Sept 1997.
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